The present invention relates to a rotor disc to shaft coupling, and more particularly to an axial mechanical coupling between a ceramic turbine rotor and a metal shaft.
Turbine inlet temperature strongly influences the thermal efficiency of a gas turbine: higher turbine inlet temperature generally leads to more thermally efficient gas turbines. However, higher turbine inlet temperature requires temperature and oxidation resistant materials such as ceramics. These components include ceramic turbine rotors that are typically attached to a metal shaft such that power is transmitted from the turbine rotor to a compressor rotor.
Connecting the ceramic turbine rotor to a metal shaft requires particular structural arrangements as ceramics thermally expand less than metals. The difference in thermal expansion results in thermal stress that may lessen the connection between the ceramic rotor and the metallic shaft. To maintain an effective joint between the rotor and the shaft, various brazing as well as mechanical clamp structures have been employed.
Brazing may be limited by the strength of the braze material and tends to soften above 900° F. Mechanical clamp structures are suited for application with higher temperatures but may be relatively complicated.
Accordingly, it is desirable to provide an uncomplicated mechanical coupling for coupling a ceramic member to a metal member that is capable of transmitting torque at relatively high temperatures.